In release 10 of LTE (Long Term Evolution), CA (Carrier Aggregation) in which a plurality of CCs (Component Carriers) under the same radio base station eNB are aggregated to perform communication as shown in part (a) of FIG. 5 has been introduced to achieve communication in a wide bandwidth exceeding 20 MHz (for example, communication of 100 MHz).
Later, Release-12 and beyond of LTE have proposed “Small Cell Enhancement”, and “Inter-site CA” in which communication is performed by aggregating CCs (cells) under different radio base stations eNB has been considered to be introduced as one of network architectures which are more flexible than conventional architectures (see part (b) of FIG. 5).
For example, the following operation is conceivable by using “Inter-site CA”. As shown in part (b) of FIG. 5, a C-plain signal for which reliability needs to be secured is communicated through a SRB (Signaling Radio Bearer) in a cell #1 (macro cell) under a radio base station eNB#1 (macro eNB), and a U-plane signal which requires broadband communication is communicated through a DRB (Data Radio Bearer) in a cell #10 (small cell) under a radio base station eNB#10 (small radio base station).
As described above, when the C-plane signal is communicated through the SRB in the cell #1 under the radio base station eNB#1 and the U-plane signal is communicated through the DRB in the cell #10 under the radio base station eNB#10, the radio base station eNB#1 is assumed to basically handle settings and connectivity between the mobile station UE and the radio base station eNB#1/radio base station eNB#10, as shown in FIG. 6.
In this case, a flexible operation (installation location and the like) of the small radio base station can be achieved by employing a configuration in which only the radio base station eNB#1 being an anchor radio base station manages the security data in the cells under the radio base stations and the radio base station eNB#10 being the small radio base station manages no security data in the cells under the radio base stations.
For example, the small radio base station can be installed at a location where a user can physically touch the small radio base station.
Moreover, since the number of nodes managing the security data is not large, complexity of a network can be reduced.